From 48572f52b1c6fe2c7e57206b063ea85980e6c00b Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Tue, 9 Nov 2021 12:15:18 -0500
Subject: [PATCH] Rewrite Fix to Still Auto-Vectorize

---
 lib/compress/zstd_compress.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index 59a216918..09f18d6d9 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -2332,12 +2332,17 @@ ZSTD_reduceTable_internal (U32* const table, U32 const size, U32 const reducerVa
     for (rowNb=0 ; rowNb < nbRows ; rowNb++) {
         int column;
         for (column=0; column<ZSTD_ROWSIZE; column++) {
+            U32 newVal;
             if (preserveMark && table[cellNb] == ZSTD_DUBT_UNSORTED_MARK) {
+                /* This write is pointless, but is required(?) for the compiler
+                 * to auto-vectorize the loop. */
+                newVal = ZSTD_DUBT_UNSORTED_MARK;
             } else if (table[cellNb] < reducerThreshold) {
-                table[cellNb] = 0;
+                newVal = 0;
             } else {
-                table[cellNb] -= reducerValue;
+                newVal = table[cellNb] - reducerValue;
             }
+            table[cellNb] = newVal;
             cellNb++;
     }   }
 }
-- 
2.47.2